The Ampeg SVT power amp tube blues

So I was putting some 70s USA Sylvanias in my SVT, and I thought, "what the hell, I've always wanted so see the rest of this thing from the inside." So I opened the back plate, pulled out the stock SOVTEK 6550's in there, and then it hits me: I've been gigging this thing for 6 months with 2 broken 6550's; one is cracked, with the grey stuff (zinc oxide?) all over it, and the other is just plain shattered. So what's the next step? Should I simply replace the 2 broken SOVTEK's or get a new set of end-all tubes? I really don't feel like shelling out the $350 it costs to retube, but I will if necessary (goodbye, Spector)

Each tube has a resistor that'll blow to protect the rest of the amp in the event of catastrophic tube blowout. I don't know much about it, but I've found it doesn't always happen when you lose a tube.

Having replaced the tubes, watch them as you come out of standby. If the tubes are operating as they should you'll see a blue glow inside the glass. That glow signifies that the tubes are passing current.

Watch also the plates. If any show signs of a red glow you need to have the bias looked at by a tech. The "red plate" means that that tube is passing too much current.

I would place the new tubes on the same side of the OPT primary. Either positions 1,2 or 3 OR 4,5,or 6.

Replace them all & take the unit to a good tube amp tech to check everything out. I just had my 1989 SVT II non pro retubed & checked by my Tube Amp Guy Joe Kolla in RVA. He is the man! I'm running 1990s NOS Svetlana SV6550s four Gold Lion 12AX7s & two NOS 1959 Amperex 12AU7s. Sounds like a Lion God with all that growl & its pumping around 350 watts. Get your stuff checked those tubes shouldnt be broken like that they should just burn out & mess up your sound. Their might be something seriously wrong with your head.